Siegel and Metman1 conclude that bilateral pallidotomy has a beneficial effect on walking speed. There are several difficulties with this conclusion.
The authors compare the mean preoperative speed with the mean postoperative speed and show that the latter speed is twice the former. However, as stated in the article, there was a highly variable individual response. Comparing means may give a misleading picture since the mean is seriously affected by extreme values.2
Pincus MM. Beneficial Effect of Bilateral Pallidotomy on Gait Is Unproven. Arch Neurol. 2000;57(8):1231. doi: